The Interplay Between Hyperthyroidism and Ovarian Cytoarchitecture in Albino Rats

Abstract

Background Hyperthyroid females often complain of menstrual disturbances and impaired fertility. This study was designed to observe the effect of hyperthyroidism on ovarian folliculogenesis and the hypophyseal-gonadal axis. Methodology Adult female Wistar albino rats (n= 12), six to eight weeks of age, and weighing 70-162 g, were divided randomly into control (Group A) and experimental (Group B) groups. Group A received daily intraperitoneal injections of 250 µL normal saline (10 µL 5 µM NaOH dissolved in it) for 14 days. Group B received a daily intraperitoneal injection of levothyroxine (600 µg/kg body weight) to induce hyperthyroidism. Rats were weighed at the start and the end of the experimental period on the day of sacrifice. Results Statistical analysis of the data revealed successful induction of hyperthyroidism in Group B as their thyroid-stimulating hormone (TSH) levels decreased significantly. The ovarian size was significantly reduced in the hyperthyroid group (p < 0.029). There was a significant decrease in thickness of the ovarian capsule (p < 0.000), an increase in the number of primordial, primary, and secondary follicles (p < 0.001, 0.000, and 0.001, respectively), and a decrease in size of primary and secondary follicles (p < 0.041 and 0.020) in the hyperthyroid group. Conclusion Hyperthyroidism can affect ovarian cytoarchitecture, probably by acting directly on its receptors and thus affects female fertility.

Keywords: fertility; hyperthyroidism; ovarian follicle; wistar rats.

Figure 1. Photomicrograph of the ovary from Group A (control), showing stromal components of the ovary. Masson’s trichrome. x100

Germinal epithelium (GE), tunica albuginea (TA), the primary follicle (PF), corpus luteum (CL), stroma (S)

Figure 2. Photomicrograph of the ovary from Group B (experimental). Thinning of the capsule/TA of the ovary can be seen. Masson’s trichrome. x100

Tunica albuginea (TA), germinal epithelium (GE), the primary follicle (PF), stroma (S)

Figure 3. Photomicrograph of the ovary from Group A (control), showing different stages of follicular development. H&E. x50

Primary follicle (PF), the secondary follicle (SF), Graafian follicle (GF), corpus luteum (CL), granulosa cells (GC), oocyte (O), hematoxylin and eosin (H&E)

Figure 4. Photomicrograph of the ovary from Group B (experimental), showing an increased number of follicles. H&E. x50

Primordial follicle (PrF), the primary follicle (PF), the secondary follicle (SF), Graafian follicle (GF), corpus luteum (CL), stroma (S), follicular antrum (FA), blood vessel (BV), hematoxylin and eosin (H&E)